Vaisala HUMICAP HMP155, User Manual, Page: 18 / 102

2.3.2.1 Automatic chemical purge (interval purge)
If you select the automatic chemical purge option, chemical purge takes place according to the
intervals set in the factory. You can change the interval with the
PUR
command. You may have
to do it, if the measuring environment contains high concentrations of interfering chemicals.
You can also turn off the automatic chemical purge.
2.3.2.2 Manual chemical purge
Perform manual chemical purge
• Always before relative humidity calibration and adjustment
• If you think the sensor has been exposed to an interfering chemical.
You can activate manual chemical purge by turning the startup purge on temporarily and
resetting the probe. After the operation, to turn off the startup purge, use the
PUR command.
Before starting calibration, make sure that the sensor temperature has reached
normal temperature.
More information
‣
Overview (page 66)
‣
PUR command (page 50)
2.3.3 Extra sensor heating (Xheat) option
You can define the humidity sensor heating temperature and the duration of the heating.
Sensor heating starts when the relative humidity of the measuring environment reaches the
RH value (RH limit) you have set.
After the heating cycle, a new sensor heating cycle is performed if the predefined conditions
are reached again.
During the sensor heating, the outputs are locked to the values measured before
the heating cycle.
HMP155 User Guide M210912EN-D
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